Microstrip gunn oscillator with varactor tuning

Abstract

A microwave oscillator arrangement comprising a microstrip resonator, a Gunn oscillator mounted outside the substrate of the resonator, a varactor diode connected in series with the Gunn oscillator and the resonator, and means for applying adjustable bias to the varactor diode.

We claim: 
     
       1. A microwave oscillator arrangement comprising a dielectric substrate, a microstrip resonator formed on a portion of the substrate, a negative-resistance oscillator device external to the resonator, means for coupling the negative-resistance oscillator device to the resonator, whereby substantially all the R.F. power produced by the negative-resistance oscillator device is fed into the resonator, means for coupling R.F. power out of the resonator into a load, and a variable reactance connected in series between the negative-resistance oscillator device and the resonator whereby to adjust the operating frequency of the oscillator arrangement. 
     
     
       2. An oscillator arrangement as claimed in claim 1 wherein the resonator is a length of microstrip line. 
     
     
       3. An oscillator arrangement as claimed in claim 2 wherein the microstrip line is open circuited. 
     
     
       4. An oscillator arrangement as claimed in claim 3 wherein the variable reactance is connected to one end of the microstrip line. 
     
     
       5. An oscillator arrangement as claimed in claim 1 wherein the means for coupling power out of the resonator comprises a capacitor. 
     
     
       6. An oscillator arrangement as claimed in claim 5 wherein the capacitor comprises a gap between the resonator and a further strip line. 
     
     
       7. An oscillator arrangement as claimed in claim 1 wherein the means for coupling R.F. power out of the resonator is immediately adjacent a connection of the means for coupling the negative-resistance device to the resonator. 
     
     
       8. An oscillator arrangement as claimed in claim 1 wherein the means for coupling the negative-resistance device to the resonator comprises a wire. 
     
     
       9. An oscillator arrangement as claimed in claim 1 wherein the variable reactance is a varactor. 
     
     
       10. An oscillator arrangement as claimed in claim 1 wherein the negative-resistance device is an unencapsulated Gunn device. 
     
     
       11. An oscillator arrangement as claimed in claim 10 wherein the Gunn device is mounted on a thermally conductive screw. 
     
     
       12. An oscillator arrangement as claimed in claim 1 comprising means for varying the reactance so as to reduce a variation of operating frequency with temperature. 
     
     
       13. An oscillator arrangement as claimed in claim 12 wherein the means for varying the reactance comprises a thermistor. 
     
     
       14. An oscillator arrangement as claimed in claim 1 comprising a distributed low-pass filter for applying a D.C. voltage to the negative-resistance device. 
     
     
       15. An oscillator arrangement as claimed in claim 1 comprising a distributed low-pass filter for applying a D.C. voltage to the variable reactance. 
     
     
       16. An oscillator arrangement as claimed in claim 1 comprising a gyromagnetic isolating device, having a plurality of ports and wherein the means for coupling R.F. power out of the resonator is arranged to couple the R.F. power into a first port of the isolating device. 
     
     
       17. An oscillator arrangement as claimed in claim 16 wherein the isolating device is a three-port circulator and wherein a mixer diode is coupled to a second port of the circulator relatively isolated from the first port. 
     
     
       18. An oscillator arrangement as claimed in claim 17 comprising a distributed low-pass filter connected to the mixer diode. 
     
     
       19. An oscillator arrangement as claimed in claim 16 wherein the isolating device is a three-port circulator and wherein a matched load is connected to a second port of the circulator relatively isolated from the first port. 
     
     
       20. An oscillator arrangement as claimed in claim 1 wherein the resonator is formed on a ferrite substrate.